Polymers of carbon monoxide and olefins, such as ethylene, have been known and available in limited quantities for many years. For example, polyketones are disclosed in Kirk-Othmer Encyclopedia of Chemical Technology, Second Edition, Vol. 12, p. 132, 1967, and in Encyclopedia of Polymer Science and Technology, 1968, Vol. 9, 397-402. It is known that polyketones may be prepared by contacting CO and ethylene monomers in the presence of a catalyst. High molecular weight polymers of ethylene which contain small quantities of carbon monoxide can be prepared with the aid of Ziegler catalysts. Low molecular weight polymers of carbon monoxide with ethylene and possibly other olefinically unsaturated hydrocarbons in which all monomer units occur distributed at random within the polymer can be prepared with the aid of radical catalysts such as peroxides. A special class of the polymers of carbon monoxide with ethylene is formed by the high molecular weight linear polymers in which the monomer units occur in alternating order and which polymers consist of units with the formula --CO--(C.sub.2 H.sub.4)--. Such polymers can be prepared with the aid of, among others, phosphorus-, arsenic-, antimony-, or cyanogen-containing compounds of palladium, cobalt or nickel as catalysts.
High molecular weight linear alternating polymers of carbon monoxide and ethylene consisting of units of the formula --CO--(C.sub.2 H.sub.4)--, can also be prepared by using catalyst compositions comprising:
(a) a compound of a Group VIII metal selected from the group consisting of palladium, cobalt and nickel. PA0 (b) an anion or a non-hydrohalogenic acid having a pKa less than 2, and PA0 (c) a bidentate ligand of the general formula ##STR1## wherein M represents phosphorus, arsenic or antimony, R is a bivalent organic bridging group containing at least two carbon atoms in the bridge and R.sup.1, R.sup.2, R.sup.3 and R.sup.4 represent hydrocarbon groups.
In the above-mentioned polymer preparation both the reaction rates and the molecular weights of the polymers obtained play a major role. On the one hand it is desirable to aim at the highest possible reaction rate in the polymer preparation, on the other hand,--with a view to their potential applicability--these polymers are more valuable with higher molecular weight. Both the reaction rate and the molecular weight can be affected by the temperature and overall pressures applied during the polymerization process. Higher reaction rates and lower molecular weights will be obtained accordingly as higher reaction temperatures are chosen. The effect which a rise in reaction temperature and overall pressure has on reaction rates is greatest at reaction temperatures below 85.degree. C. and overall pressures below 75 bar. Above these values increased reaction temperatures and overall pressures will still lead to higher reaction rates but the increase will become increasingly smaller.
In view of the above, polymers of carbon monoxide and ethylene used to be prepared mainly at a reaction temperature in the range of from 60.degree. to 70.degree. C. and at an overall pressure in the range of from 50 to 60 bar. A correct choice of reaction temperatures and overall pressures within the said ranges allowed polymers of sufficiently high molecular weights for the relevant application to be produced at acceptable reaction rates. Attempts to achieve an increase in reaction rate by varying the ratio between the ethylene partial pressure and the carbon monoxide partial pressure remained unsuccessful. At overall pressures below 75 bar variations in the ratios between ethylene partial pressure and carbon monoxide partial pressure ranging from 0.3 to 3 did not lead to any significant change in the reaction rate. Variations of the partial pressure ratios within the same range did not have any significant influence on the molecular weights of the polymers obtained either.